Method of and apparatus for starting alternating-current motors.



M. KORNMRPBR. METHOD OF AND APPARATUS FOR STARTING ALTERNATING CURRENT MOTORS.

Patented May 19, 1914.

fig. 5

APPLIDATION FILED MAY 15, 1908.

WITNESSES JAZYL'NTUR 2 g W MAX KuRzsmfiHz-L'R.

MQW- 5 1644 AT Y subject of the King of Prussia and MAX xommominn, or

mn'rnon or AND Arramr-us roaspeciflcation'of Letters Patent. Application filed May 15, 1908. Serial No. 433,065.

PANKOW, GERMANY, ASSIGNOR- T0 GENERAL ELECTRIC 00.,

A CORPORATION OF'NEW YORK.

STARTING A LTEBNATING-CURRENT MOTORS.

Patented May 19, 1914.

To all whom it may concern Be it known that I, Max KoRNooRrnE, a

mperor of Germany, residing at Pankow, Germany, have invented certain new and useful Improvements in Methods of and Appa ratus for Starting Alternating-Current Motors, of which the following is a specificatron;v

My invention relates to the starting'of electric motors, and more particularly to the starting of alternating current motors, which are started by means of a compensator for impressing a voltage-lower than the line voltage upon the motor terminals which are subsequently connected to the full line voltage, and has forits object an improvement in this method ofv starting motors.

In the past it has been customary to start alternating current motors with a compensutor, which has an intermediate tap or taps to which the motor terminals are connected, and after the motor has obtained nearly its full speed, its terminals may be connected directly to the full line voltage. advantage of this method is that there is a sudden rush of the current taken by the motor when the starting switch or controller is altered so as to change the connections of the motor terminals from one intermediate tap to another'on the compensator, or to full'line voltage, since, when the circuit is interrupted the motor loses' more or less of its magnetization and hence when the current is renewed after this interruption, it will be renewed with a sudden rush. In case it is desired to avoid this sudden rush of current, choke coils mag; be introduced which can be switched into the motor circuit between the time of connecting its terminals from one voltage to the next succeeding higher voltage, and thus there will be no interruption'in' the current, the motor will lose. none of its magnetization and hence there will be no sudden increased rush ofcurrent. If either of these ,methodsbe used the apparatus is complicated and costly, ing the motor, large, or if a number of steps beus'ed, while the .ch'oking coils may besm'all'er, the switch must be complicated and hence expensive.

The objects of my invention are then to and the motor terminals. ,a voltage to be impressed upon the motor The dis- 1 since if, only one step be used in'startthe choke coils used must be provide a method ofand a device for starting alternating current motors without an inter- -'ruption in the starting current, or without the use of the expensive and complicated apparatus which has been used in the past, for avoiding thls rush of current. I accomplish this object by the use of a starting compensator or electromotive force regu lating device, which is so arranged that after the motor is started by connecting its terminals to taps of the starting compensator that will give a voltage lower. than the line voltage upon the motor terminals, the'compensator or electromotive force regulating device is connected so as to become a reactive coil in series between the line voltage This will cause terminals intermediate that impressed by the startlng taps 'on the compensator and the .full line voltage, since only about one-half the number of windings of the compensator will be eiiective as a reactive coil, and since the compensator or starting transformer may be wound for a high saturation on account of the short period oi? its opera. 'tion. The motor will then receive a somewhat higher impressed voltage than that given by the low voltage taps on the compensator or electromotive force regulating device, and its terminals may then be connected directly to the line voltage byshort circuiting that portion of the compensator used as a reactive coil. The current will therefore rise without any'sudden rush, since the. motor at no tlme has lost its magnetization or its torque.

For further understanding of my invention, reference" may be had to the accompanying drawing wherej Figurel shows dia ammatically the 01rcuits for starting a t ree phase motor with my new method; Figs. 2, 3 and 4 show diagrammatically ous steps used in starting the motor; and Figs. 5 and 6 show a, modification. which may beintroduced into the method of startlIl. '7 Y 'ileferringfirst to Fig. 2, I have shown a three pha'se:autotransformer compensator or electromotive force "regulating device C, which has terminals 1, 2 and 3 which may the connections for the vari- I be connected to a suitable source of alternating currentsupply. 1 is an alternating current motor which I have shown as a three phase induction motor, but it will be obvious that other forms of motor may be used. Compensator or electromotive force regulating device C is wound for a threephase circuit and is Y connected by means of conductors 4 and 5 by which I mean that the windings of the compensator are connected together by these conductors to form what is commonly known as a neutral point. The device C has intermediate taps 6, 7 and 8, which in starting, are connected to the field winding F of the motor 1. After the motor hasattained a considerable speed, connections 4: and 5 are broken, that is, the

neutral point of the compensator or elec terminals of the motor connected directly,

tromotive force regulating device is opened, so that the circuits will be as shown in Fig. 3 and the compensator or electromotive force regulating device will act as a three-phase reactive. coil in series between the source of supply and the motor. After a desired length of time has elapsed, that portion of the compensator or electromotive force regulating device winding which acts as a re active coil, may be short circuited and the to the line voltage, as shown in Fi 4.

Figs. 5 and 6 showa modification of the above described connections, in that after thecompensator or electromotive force regulating device has been connected so as to act as a reactive coil, instead of connecting the motor terminals directly to the line voltage, they may be connected in series with voltage consuming devices 9, shown in Fig. 5, so as to make the gradation in voltage between the and 6 less than that shown between Figs. 3 and 4. I Subsequent to the connection shown in Fig. 5 the voltage consuming devices 9 may be short circuited as shown in I Fig. 6, when the motor will be running with as having its terminals connected to the full line voltage with the same connection as shown in Fig. 4.

Fig. 1 shows a diagram of connect-ions.

for making the steps described, In a simple manner, by the use. of a controller T,

AB and C and a three-phase switch S.

from a suitable are line conductors fed supply. Controller. T is formed in the well nown manner with stationary fingers 10 and movable contacts 11 and 12 and is shown three positions diagrammatically marked y the lines'P P and P Comg'ensator or electromotive force regulating ev1ce Chas its terminals 1, 2 an 3 connected to a switch S and its intermediate "voltage tapsand"the connections for joinmg its neutral point connected to fingers 1O 6" of controller T. There are also connections between terminalsl, 2 and 3 and fingers 10 steps shown in Figs. 5'

on the controller. If switch S be closed sition so that contact 11 closes the neutral point of'the compensator or electromotive forceregulating device, the motor will start up with a reduced voltage derived from the compensator or electromotive force regulating device. If the controller be now moved into' position shown by 1? so that there will be no movable contacts connecting fingers 10, the neutral point of the compensator'will be opened and the compensator will act as a reactive coil in series with the motor. When the controller is moved into position shown "by P so that contacts 12 make contact with fingers 10, full line voltage will be impressed upon the motor terminals as the running condition forthe motor. I

While I have described a certain succession of connections, I may, if I so desire, start the motor with the neutral pointof the compensator or electromotive force regulating device opened and then cl'ose 'the neutral point so that the compensator will act as a compensator and then'use the successive connections'previously described.

-The advantage of first connecting the compensator as a reactive coil instead of a compensator, is that it causes a lower voltage to be impressed upon the motor terminals than would be the case,for the connection with the neutral poin of the compensator closed, and this m y be advantageous in the starting of high voltage motors. The reason that a low voltage will be impressed upon the motor terminals with the neutral point of the compensator open, is that the short circuit current ofthe motor will be greatlyinexcess of the normal current or the no load current, and this will cause the voltage drop upon that portion of the compensator used as a reactive coil to be much in excessof the voltage across the motor. This voltage drop across the compensator used asa reactive coil may be so connection, but will have a certain voltage impressed upon it. But'when the next step is taken in starting the motor, that is when the neutral point of the compensator is made, a suflicient voltage will be impressed great that the motor willnot start with this a upon the motor terminals to start the motor without the large change of'voltage which results if the motor terminals be directly connected to.the intermediate tap on the compensator with its neutral point connected sothat it acts as 'a compensator. In starting a motor with this latter-succession .of steps the switch S, Fig. 1 would be thrown without moving the controller T. 1

The circuits would then be as shown in-Fig.

3'. The controller would then bethrown to it various successive points so that the conn tions shown in Figs. 2, 3 and 4 would sucart that while I have described my invention' as applied to a three phase motor it may be also applied to motors of other numbers of phases.

\Vhile I have described a certain method and arrangement of connections, I do not limit myself to this method and arrangement, but seek in the appended claims to cover all those methods and arrangements. which will be obvious to those skilled in the art that may be included Within the scope of my invention. I

What I claim as new and desire to secure by Letters Patent of the United States, is,

1. The method. of operating an electromotive force regulating device for starting electrical apparatus from a source of supply, consisting in connecting it at onetime as a reactive coil and at another time as a compensator between the apparatus and the 2. The method of operating an electromotive force regulating device for starting electrical apparatus from asource of supply, which consists in connecting it successively as a reactive coil, then as a coinmy hand this 30 pensator, and then again as a reactive coil between the apparatus and the source.

1 3. The method of operating an electromotive force regulating device for starting electrical apparatus from a source of supply, which consists in connecting it succes sively as a reactive coil and thenas a com pensator between the apparatus and the a 4. The method of operating an electro motive force regulating. device for starting electrical apparatus from a source of supply, which consists in connecting it successively as a compensator and then as a reactive coil between theapparatus and the source.

5. The method of operating electrometive force regulating devices having their windings adapted to be connected'together to form a neutral point and having taps intermediate the terminals of the windings, for starting electrical apparatus consisting in connecting the apparatus to the taps, then opening the neutral point of the device and then connecting full line voltage to the apparatus.

In witness whereof, I have hereunto set day of April, 1998. MAX KORNDORFER. Witnesses:

ALFRED KRAusn, HANS AGKERMAN. 

